Chronic kidney disease (CKD) affects >10% of the adult US population, costs tens of billions of dollars annually, and can lead to progressive kidney failure, cardiovascular disease (CVD), and early mortality. Although we understand much about the epidemiology of CKD, the underlying mechanisms of CKD initiation and progression remain less well understood. In this proposal, which represents a continuation of Phase 1 of the CKD Biomarker Consortium, we seek to test the ability of promising biomarkers of kidney injury to predict CKD incidence and progression in non-proteinuric and proteinuric individuals; furthermore, we propose serving as a development, quality control, and validation site for biomarker measurements for the Consortium. We propose measurement of novel biomarkers of tubular injury and inflammation, two key pathways of injury that we hypothesize are associated with CKD progression in both diabetic- and non-diabetic kidney disease. Biomarkers to be tested included kidney injury molecule-1, a transmembrane glycoprotein expressed almost exclusively in the proximal tubule in response to injurious stimuli; urinary complement fragments, which were identified as promising biomarkers in Phase 1 of CKD BioCon; and soluble tumor necrosis factor-a receptors 1 and 2 (sTNFR1 and sTNFR2). We will measure biomarkers approved by the Consortium and external expert panel in unique prospective cohort studies: the Framingham Heart Study (FHS), a prospective study of over 2,948 individuals with available baseline plasma samples and follow-up data over more than one decade; two other community-based cohort studies from Uppsala, Sweden, ULSAM (N = 778) and PIVUS (N = 815); the Renin-Angiotensin System Study (RASS), comprised of 254 T1D participants aged 16-65 years who underwent kidney biopsy for research purposes at baseline and after 5 years of follow-up with blood and urine samples collected every six months; the Pima Indian Cohort of 260 participants (111 biopsied at end of study) with type 2 diabetes mellitus (T2D) with available plasma and urine samples collected every two years during a median follow-up of 10 years; and the Boston Kidney Biopsy Cohort (U01DK093574, ancillary study to CKD Biomarkers Consortium), an ongoing prospective study (N = 649 to date) in which blood and urine samples are obtained at the time of native kidney biopsy. In Aim 1 we will test whether biomarkers, independently of albuminuria and eGFR, are associated with future development of incident CKD or CKD progression. In Aim 2, we will test the associations of biomarkers with histopathologic findings on kidney biopsy. In Aim 3, we propose establishing Brigham and Women's Hospital as a core laboratory for biomarker measurements for the Consortium and to continue of our efforts to ensure reliable quality control and validation of assays in use across the Consortium.